阅读说明：本技术 金属冶炼分离联产高纯钙产品的方法及其制备的高纯钙产品 (Method for metal smelting separation and co-production of high-purity calcium product and high-purity calcium product prepared by method ) 是由 冯宗玉 陈世梁 王猛 黄小卫 徐旸 彭新林 孙旭 夏超 赵岩岩 魏煜青 于 2019-11-06 设计创作，主要内容包括：本发明属于金属冶炼分离技术领域,具体涉及一种金属冶炼分离联产高纯钙产品的方法,并进一步公开其制备的高纯钙产品,所述高纯钙产品包括高纯二水氯化钙、无水氯化钙、碳酸钙。本发明所述的金属冶炼分离联产高纯钙产品的方法,以金属冶炼分离过程中产生的含氯化镁废水为原料,通过与含氢氧化钙的浆液进行碱转反应,得到非钙杂质元素含量极低的氯化钙溶液及滤饼,而制得的氯化钙粉末通过与水蒸气在一定条件下进行高温热解,可得到高纯氧化钙粉末,再经碳化法制备碳酸钙,获得产品的纯度较高。本发明所采用的高纯碳酸钙的生产方法使用简单的手段从根本上解决了高纯碳酸钙制备中杂质对产品质量的影响,提高碳酸钙产品稳定性。(The invention belongs to the technical field of metal smelting separation, particularly relates to a method for metal smelting separation and coproduction of high-purity calcium products, and further discloses high-purity calcium products prepared by the method, wherein the high-purity calcium products comprise high-purity calcium chloride dihydrate, anhydrous calcium chloride and calcium carbonate. The method for coproducing high-purity calcium products by metal smelting separation takes magnesium chloride-containing wastewater generated in the metal smelting separation process as a raw material, and performs an alkali conversion reaction with slurry containing calcium hydroxide to obtain a calcium chloride solution with extremely low content of non-calcium impurity elements and a filter cake, and the prepared calcium chloride powder is subjected to high-temperature pyrolysis with water vapor under certain conditions to obtain high-purity calcium oxide powder, and then the calcium carbonate is prepared by a carbonization method, so that the obtained product has high purity. The production method of the high-purity calcium carbonate adopted by the invention fundamentally solves the problem of influence of impurities on the product quality in the preparation of the high-purity calcium carbonate by using a simple means, and improves the stability of the calcium carbonate product.)

1. The method for metal smelting separation and coproduction of high-purity calcium products is characterized by comprising the following steps:

(1) adding calcium hydroxide-containing slurry into magnesium chloride-containing wastewater generated by extraction treatment in the metal smelting separation process, uniformly mixing, carrying out alkali conversion reaction, and filtering to obtain a high-purity calcium chloride solution and a magnesium hydroxide-containing filter cake;

(2) concentrating the prepared high-purity calcium chloride solution, and performing spray dehydration to obtain a high-purity calcium chloride product; the obtained magnesium hydroxide-containing filter cake is carbonized to prepare a solution containing magnesium bicarbonate, and the solution is circulated to the metal smelting separation process in the step (1);

(3) and (3) carrying out pyrolysis reaction on the high-purity calcium chloride product prepared in the step (2) to obtain high-purity calcium oxide powder and hydrogen chloride gas, absorbing the hydrogen chloride gas by dilute hydrochloric acid or water to prepare hydrochloric acid, and circulating the hydrochloric acid to the metal smelting separation process in the step (1).

2. The process for separating and co-producing high purity calcium product by metal smelting according to claim 1, wherein in the step (1):

the metal smelting separation step comprises the smelting separation of rare earth metal, metal nickel and/or metal cobalt.

3. The process for separating and co-producing high purity calcium product by metal smelting according to claim 1 or 2, wherein in the step (1):

controlling the molar concentration of the magnesium chloride-containing wastewater to be 0.5-4 mol/L;

controlling the molar ratio of the magnesium chloride in the magnesium chloride-containing wastewater containing the impurities to the calcium hydroxide in the calcium hydroxide slurry to be 0.85-0.98: 1.

4. The process for separating and co-producing high purity calcium product through metal smelting according to any one of claims 1 to 3, wherein the step (1) further comprises the step of preparing the slurry containing calcium hydroxide from one or more of limestone, lime and dolomite through calcination and digestion.

5. The process for separation and co-production of high purity calcium product by metal smelting according to any one of claims 1 to 4, wherein in the step (2), the spray dehydration step comprises: spray-dehydrating the obtained high-purity calcium chloride solution at 120 ℃ to obtain high-purity calcium chloride dihydrate, and/or spray-dehydrating the obtained high-purity calcium chloride solution at 300 ℃ to obtain high-purity anhydrous calcium chloride.

6. The method for metal smelting separation and coproduction of high-purity calcium products as defined in any one of claims 1 to 5, wherein in the step (3), the temperature of the pyrolysis reaction is controlled to be 800-1000 ℃, the pyrolysis time is 0.5-2.5h, and the reaction pressure is 0.2-0.4 MPa.

7. The process for separating and co-producing high-purity calcium product by metal smelting according to any one of claims 1 to 6, wherein in the step (3), the pyrolysis reaction is carried out in an atmosphere of hydrogen chloride and water vapor; and control (X)_{Hydrogen chloride})²/X_{Steam of water}＝3.28×10^-5-2.178×10^-4Wherein X is_{Hydrogen chloride}、X_{Steam of water}Respectively representing the percentage of hydrogen chloride gas and the percentage of water vapor in the atmosphere.

8. The method for metal smelting separation and coproduction of high-purity calcium products as claimed in any one of claims 1 to 7, wherein the method further comprises the steps of slurrying the high-purity calcium oxide powder prepared in the step (3) and preparing high-purity calcium carbonate through carbonization reaction; and/or, the carbon dioxide produced in the metal smelting separation step in the step (1) is used in the step of the carbonization reaction.

9. The method for separating and co-producing high-purity calcium products in metal smelting according to claim 8, further comprising the steps of inputting the water vapor collected in the spray dehydration step in the step (2) into the step (3) for pyrolysis reaction, and collecting the condensed water vapor in the step (3) for subsequent high-purity calcium oxide powder slurry mixing.

10. The high-purity calcium product prepared by the method for separating and co-producing high-purity calcium products in metal smelting according to any one of claims 1 to 8, wherein the high-purity calcium product comprises high-purity calcium carbonate, high-purity calcium chloride dihydrate and/or high-purity anhydrous calcium chloride;

the calcium chloride content of the high-purity calcium chloride dihydrate is more than or equal to 77.0 wt%, the total magnesium content is less than 0.005 wt% calculated by magnesium chloride, and the iron content is less than 0.0001 wt%;

the calcium chloride content of the high-purity anhydrous calcium chloride is more than or equal to 97.0 wt%, the total magnesium content is less than 0.005 wt% calculated by magnesium chloride, and the iron content is less than 0.0001 wt%;

the calcium carbonate content of the high-purity calcium carbonate is more than or equal to 98.0 wt%, the total magnesium content is less than 0.005 wt% calculated by magnesium chloride, and the iron content is less than 0.0001 wt%.

Technical Field

The invention belongs to the technical field of metal smelting separation, particularly relates to a method for metal smelting separation and coproduction of high-purity calcium products, and further discloses high-purity calcium products prepared by the method, wherein the high-purity calcium products comprise high-purity calcium chloride dihydrate, anhydrous calcium chloride and calcium carbonate.

Background

Among calcium salt products, calcium carbonate and calcium chloride are two most common calcium salt products, and have wide application in various industrial productions. The calcium carbonate is widely applied to the fields of rubber, plastics, wires, cables, coatings, papermaking, printing ink and the like. The calcium chloride product is divided into calcium chloride dihydrate and anhydrous calcium chloride according to the content of crystal water, and the main products of the calcium chloride dihydrate and the anhydrous calcium chloride which are taken as calcium salts can be divided into industrial-grade calcium chloride and food-grade calcium chloride according to grades, wherein the industrial-grade calcium chloride can be used as a refrigerant, an antifreezing agent, a drying and dehydrating agent, a flame retardant, a filling agent and raw materials for producing other calcium salt products, and the additional value of the commercial product is relatively low (the domestic market of the industrial-grade calcium chloride product is 700-plus 900 yuan/ton); the food-grade calcium chloride can be used as a stabilizer, a thickening agent, a moisture absorbing agent and a taste modifier for food processing, is also applied to the synthesis and preparation of special medicines, has higher added value (the domestic market price of the food-grade calcium chloride product is 1650 yuan/ton), and has better market development prospect.

One of the main problems restricting the industrial development of high-purity calcium carbonate in China at present is that chemical components such as iron, magnesium, silicon-aluminum compounds, heavy metals and the like in the product are difficult to control stably. At present, the main domestic methods for preparing high-purity calcium carbonate include a double decomposition method and a carbonization method.

The double decomposition method is to prepare calcium carbonate with a certain form by using water-soluble calcium salt and water-soluble carbonate as raw materials and adding proper additives to perform double decomposition reaction under proper conditions. It is common in industry to mix a refined calcium chloride solution with ammonia carbonate, or to introduce ammonia gas and carbon dioxide into the refined calcium chloride solution to produce a solution of calcium carbonate and ammonium chloride under certain conditions. However, the calcium carbonate precipitate prepared by the method absorbs more chloride ions, a large amount of water and production time are consumed to wash away the included chloride ions, and a large amount of ammonia nitrogen wastewater is discharged in the production process, so that the surrounding environment is greatly influenced, and the production cost is increased.

The carbonization method is to obtain calcium carbonate by carbonizing calcium hydroxide suspension prepared by taking limestone as a raw material, and the main process flow comprises the following steps: calcining limestone to obtain calcium oxide, digesting kiln gas and calcium oxide, separating and removing impurities to obtain pure calcium hydroxide suspension, introducing carbon dioxide gas into the suspension, adding a proper amount of additive, carbonizing to the end point to obtain calcium carbonate slurry meeting the requirements, and dehydrating, drying and performing surface treatment on the slurry to obtain a calcium carbonate product. The carbonization method can be classified into an intermittent carbonization method, a continuous spray carbonization method and an intermittent hypergravity carbonization method according to different carbonization processes and devices. However, because the pH value of the calcium hydroxide suspension is high, metal impurities, silicon, unburned limestone slag and the like are difficult to completely remove in the purification process, and the influence of the impurities brought by limestone on the product quality cannot be fundamentally solved, so that the product is difficult to meet the requirement of high-purity calcium carbonate. Therefore, the impurity content control before carbonization plays an important role in preparing high-purity calcium carbonate, and the key step for obtaining high-purity calcium chloride is also the step for obtaining high-purity calcium carbonate.

Meanwhile, in the production process of high-purity calcium carbonate, steam is needed for pyrolysis, and hydrogen chloride gas is generated at the same time; in addition, an alkaline filter cake is generated in the alkali conversion process, and carbon dioxide is needed in the carbonization process. The problems that the byproducts are difficult to treat exist, energy is wasted, serious environmental pollution is caused, and the byproducts have no recycling value. Therefore, it is desirable to find a method for recycling by-products in the production of high purity calcium carbonate in view of the atom economy of the reaction and the production cost.

The current calcium chloride products in China are prepared differently according to industrial grade products and food grade products, wherein: the industrial-grade calcium chloride mainly takes sodium chloride and calcium chloride-containing soda ash wastewater of alkali plants in coastal areas of southeast as a raw material, and is subjected to processes of evaporation (direct evaporation, natural evaporation of a salt pan), separation and purification and the like, the method is simple in preparation of industrial calcium chloride, but sodium salt and other metal impurity elements of the obtained calcium chloride product are difficult to remove, and the product quality is influenced; the food-grade calcium chloride is mainly prepared by using hydrochloric acid and limestone as raw materials through the steps of acid dissolution, sedimentation, neutralization, filtration, multi-effect evaporative crystallization, drying and the like, wherein the content of heavy metal elements in the raw materials of the limestone and the hydrochloric acid directly determines the quality stability of a product. As can be seen, the food-grade calcium chloride product has higher requirements on the quality of raw materials.

Therefore, a method for preparing high-purity calcium chloride and calcium carbonate products with less byproducts, low impurity content of the products and no pollution is needed to be found, and the method has important industrial significance.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is to provide a method for metal smelting separation and co-production of high-purity calcium products;

the second technical problem to be solved by the invention is to provide a high-purity calcium carbonate, high-purity calcium chloride dihydrate and/or high-purity calcium chloride dihydrate product with extremely low impurity content.

In order to solve the technical problem, the method for metal smelting separation and coproduction of high-purity calcium products comprises the following steps:

(1) adding calcium hydroxide-containing slurry into magnesium chloride-containing wastewater generated by extraction treatment in the metal smelting separation process, uniformly mixing, carrying out alkali conversion reaction, and filtering to obtain a high-purity calcium chloride solution with extremely low content of non-calcium impurity elements and a filter cake containing magnesium hydroxide;

(2) concentrating the prepared high-purity calcium chloride solution, and performing spray dehydration to obtain a high-purity calcium chloride product; the obtained filter cake containing the magnesium hydroxide is carbonized to prepare a solution containing the magnesium bicarbonate, and the solution is circulated to the metal smelting separation process in the step (1);

(3) and (3) carrying out pyrolysis reaction on the high-purity calcium chloride product prepared in the step (2) to obtain high-purity calcium oxide powder and hydrogen chloride gas, absorbing the hydrogen chloride gas by dilute hydrochloric acid or water to prepare hydrochloric acid, and circulating the hydrochloric acid to the metal smelting separation process in the step (1).

In the step (1):

the metal smelting separation step comprises the smelting separation of rare earth metal, metal nickel and/or metal cobalt.

In the step (1):

controlling the molar concentration of the magnesium chloride-containing wastewater to be 0.5-4 mol/L;

controlling the molar ratio of the magnesium chloride in the magnesium chloride-containing wastewater to the calcium hydroxide in the calcium hydroxide slurry to be 0.85-0.98: 1.

In the step (1), the temperature of the alkali-transfer reaction is 25-60 ℃, and the reaction time is 0.5-2.5 h.

The step (1) also comprises a step of preparing the slurry containing the calcium hydroxide by calcining and digesting one or more of limestone, lime and dolomite.

In the step (2), the spray dehydration step includes: spray-dehydrating the obtained high-purity calcium chloride solution at 120 ℃ to obtain high-purity calcium chloride dihydrate, and/or spray-dehydrating the obtained high-purity calcium chloride solution at 300 ℃ to obtain high-purity anhydrous calcium chloride.

In the step (3), the temperature of the pyrolysis reaction is controlled to be 840-960 ℃, the pyrolysis time is 0.5-2.5h, and the reaction pressure is 0.2-0.4 MPa.

In the step (3), the pyrolysis reaction is carried out in an atmosphere of hydrogen chloride and water vapor; and control (X)_{Hydrogen chloride})²/X_{Steam of water}＝3.28×10^-5-2.178×10^-4Wherein X is_{Hydrogen chloride}、X_{Steam of water}Respectively representing the percentage of hydrogen chloride gas and the percentage of water vapor in the atmosphere.

The method for metal smelting separation and coproduction of high-purity calcium products also comprises the step of mixing the high-purity calcium oxide powder prepared in the step (3) into slurry and preparing high-purity calcium carbonate through carbonization reaction; and/or, the carbon dioxide produced in the metal smelting separation step in the step (1) is used in the step of the carbonization reaction.

Specifically, the carbonization reaction comprises one of a batch carbonization method, a continuous spray carbonization method and a batch hypergravity carbonization method.

The method for metal smelting separation and coproduction of high-purity calcium products further comprises the step of inputting the water vapor collected in the spray dehydration step in the step (2) into the step (3) for pyrolysis reaction, and the step of collecting the water vapor in the step (3) for subsequent high-purity calcium oxide powder size mixing after condensation.

The invention also discloses a high-purity calcium product prepared by the method for metal smelting separation and coproduction of the high-purity calcium product, wherein the high-purity calcium product comprises high-purity calcium carbonate, high-purity calcium chloride dihydrate and/or high-purity anhydrous calcium chloride;

the calcium chloride content of the high-purity calcium chloride dihydrate is more than or equal to 77.0 wt%, the total magnesium content is less than 0.005 wt% calculated by magnesium chloride, and the iron content is less than 0.0001 wt%; the purity of the calcium chloride dihydrate is far higher than the GB/T26520-2011 requirement, and can meet the GB1886.45-2016 requirement of a food-grade calcium chloride product;

the calcium chloride content of the high-purity anhydrous calcium chloride is more than or equal to 97.0 wt%, the total magnesium content is less than 0.005 wt% calculated by magnesium chloride, and the iron content is less than 0.0001 wt%; the purity of the anhydrous calcium chloride is far higher than the GB/T26520-2011 requirement, and can meet the GB1886.45-2016 requirement of a food-grade calcium chloride product;

the calcium carbonate content of the high-purity calcium carbonate is more than or equal to 98.0 wt%, the total magnesium content is less than 0.005 wt% calculated by magnesium chloride, and the iron content is less than 0.0001 wt%; the purity of the calcium carbonate is far higher than the national standard GBT 19590-2011.

The method for metal smelting separation and coproduction of high-purity calcium products takes magnesium chloride-containing wastewater generated after extraction saponification treatment in the metal smelting separation process as a raw material, and performs alkali conversion reaction with slurry containing calcium hydroxide to obtain a calcium chloride solution with extremely low content of non-calcium impurity elements and a filter cake, wherein magnesium ions are completely converted into hydroxides by controlling and controlling the metering ratio of magnesium and calcium in the alkali conversion process, the alkali conversion temperature, the pH value and other conditions, and the obtained magnesium hydroxide colloid has very strong adsorption capacity of impurities such as heavy metal particles and the like, so that impurities such as iron, aluminum, silicon, heavy metals and the like enter a filter residue part to obtain a low-impurity calcium chloride solution; the hydroxide slurry is usually colloidal and has certain impurity adsorption capacity, so that the prepared calcium chloride solution has extremely low impurity content, and high-purity calcium chloride powder with extremely low heavy metal content can be obtained only by evaporation and crystallization, so that the calcium chloride solution not only can be used as an industrial calcium chloride product, but also can be used as a high-quality calcium source raw material for preparing a food-grade calcium chloride product with high added value; the prepared calcium chloride powder is subjected to high-temperature pyrolysis with water vapor under certain conditions, and because no new impurity is introduced in the pyrolysis process, high-purity calcium oxide powder can be obtained, and then the calcium carbonate is prepared by a carbonization method, so that the obtained product has high purity. The production method of the high-purity calcium carbonate adopted by the invention fundamentally solves the problem of influence of impurities on the product quality in the preparation of the high-purity calcium carbonate by using a simple means, and improves the stability of the calcium carbonate product.

On the other hand, the production method of the high-purity calcium product is combined with the metal smelting separation process, and the by-products in the production process are combined with the metal smelting separation process in the scheme of the invention, so that the resource recycling is realized, no waste water or waste gas is discharged in the whole process, and the economic benefit is effectively improved. Mixing, carbonizing and filtering the obtained by-product hydroxide suspension in the reaction process to obtain bicarbonate solution for smelting and separating rare earth; returning a part of the magnesium chloride-containing wastewater obtained by metal smelting separation to slake alkali conversion, and returning a part of the magnesium chloride-containing wastewater to be used for size mixing of magnesium hydroxide; carbon dioxide gas generated by calcining the raw material and smelting and separating metal returns to the carbonized hydroxide and the calcium oxide; the water vapor generated by calcium chloride evaporation crystallization is used for calcium chloride high-temperature hydrolysis and calcium oxide dissolution to prepare calcium hydroxide suspension. That is, other products generated in the process of preparing calcium carbonate are combined with the metal smelting separation process, so that water and gas are recycled in the whole process, and zero discharge of waste water and waste gas is realized.

According to the scheme of the invention, calcium carbonate is prepared by preferably using calcium-magnesium compounds as raw materials, and the impurity content of the obtained calcium chloride powder is lower than the calcium chloride product grade standard GB/T26520-2011, so that the calcium chloride powder plays an important role in preparing high-purity calcium carbonate. The final product calcium carbonate and the main impurity content (mass fraction): CaCO₃More than or equal to 98 percent, less than or equal to 0.5 percent of MgO, less than or equal to 5ppm of Fe, less than or equal to 5ppm of Mn, and other technical performance indexes meet the relevant requirements in the national standard GB/T19590-2011: the average grain diameter (nm) of an electron microscope is less than or equal to 60-90; BET specific surface area (m)²/g) is more than or equal to 24-30; the water content (percent) is less than or equal to 1.3; the pH value is less than or equal to 9.5; fluidity (mm): 28-36; transparency: is slightly transparent; the fineness (mum) is less than or equal to 20. The main impurity content and other technical performance indexes of the obtained high-purity calcium carbonate meet the requirements of relevant national standards.

Drawings

In order that the present disclosure may be more readily and clearly understood, the following detailed description of the present disclosure is provided in connection with specific embodiments thereof and the accompanying drawings, in which,

FIG. 1 is a process flow diagram of the method for metal smelting separation and coproduction of high-purity calcium products.

Detailed Description

The objects and/or solutions described in the present invention will be presented in the form of preferred embodiments. The description of these embodiments is for the purpose of understanding the invention and is not intended to limit the invention to other embodiments which may be practiced or carried out in accordance with the invention.

The present invention will be further illustrated by the following examples, but it is apparent that the scope of the present invention is not limited to the following examples.

As shown in a process flow diagram of figure 1, the method for metal smelting separation and coproduction of high-purity calcium product comprises the following steps:

(1) adding calcium hydroxide-containing slurry into magnesium chloride-containing wastewater generated by extraction treatment in the metal smelting separation process, uniformly mixing, carrying out alkali conversion reaction, and filtering to obtain a high-purity calcium chloride solution with extremely low content of non-calcium impurity elements and a filter cake containing magnesium hydroxide;

(2) concentrating the prepared high-purity calcium chloride solution, and performing spray dehydration to obtain a high-purity calcium chloride product; the obtained magnesium hydroxide filter cake is carbonized to prepare a magnesium bicarbonate solution; and circulating to the extraction separation in the metal smelting separation process in the step (1); simultaneously collecting the water vapor generated in the spray dehydration step;

(3) carrying out pyrolysis reaction on the high-purity calcium chloride product prepared in the step (2) to obtain high-purity calcium oxide powder and hydrogen chloride gas, absorbing the hydrogen chloride gas by dilute hydrochloric acid or water to prepare hydrochloric acid, and circulating the hydrochloric acid to extraction separation in the metal smelting separation process in the step (1); carrying out pyrolysis reaction on the water vapor collected in the step (2); collecting water vapor in the pyrolysis reaction;

(4) condensing the water vapor collected in the step (3) to obtain water, adding the prepared high-purity calcium oxide powder for size mixing, and carrying out carbonization reaction to obtain high-purity calcium carbonate;

(5) the magnesium chloride-containing wastewater and carbon dioxide are obtained in the metal smelting separation process in the step (1); and the obtained carbon dioxide is used for the carbonization reaction involved in the whole reaction to realize the circulation of the whole process.

Examples 1-3 preparation of high purity calcium chloride dihydrate

The method for preparing high-purity calcium chloride dihydrate in examples 1 to 3 comprises the following steps:

(1) adding calcium hydroxide-containing slurry into magnesium chloride-containing wastewater generated by extraction treatment in the metal smelting separation process, uniformly mixing, carrying out alkali conversion reaction, and filtering to obtain a high-purity calcium chloride solution with extremely low content of non-calcium impurity elements and a magnesium hydroxide filter cake;

(2) and concentrating the prepared high-purity calcium chloride solution, and performing spray dehydration to obtain a high-purity calcium chloride dihydrate product.

The parameters and raw materials for preparing calcium chloride dihydrate in each example are shown in table 1 below, and the product indexes of the prepared calcium chloride dihydrate product are shown in table 2 below.

TABLE 1 parameters and raw materials for the preparation of calcium chloride dihydrate

TABLE 2 product indices of the calcium chloride dihydrate product

Taking the parameters in the above example 3 as examples, the method for preparing high-purity calcium chloride dihydrate comprises the following steps: 500g of limestone is roasted at 930 ℃ for 3h to obtain calcium oxide-containing powder, 110g of the calcium oxide-containing powder is taken to be digested and reacted with 1L of pure water for 1h to obtain calcium hydroxide slurry with the calcium content (calculated by calcium oxide) of about 100 g/L. 500mL of prepared calcium hydroxide slurry is mixed and reacted with 350mL of rare earth smelting magnesium chloride solution with the concentration of 2.5mol/L, in the reaction process, the molar ratio of the added magnesium chloride to the added calcium oxide is Mg/Ca of 0.98, the reaction time is 2.5h, the reaction temperature is 30 ℃, 127g of magnesium hydroxide filter cake and 960mL of calcium chloride filtrate with the concentration of 95.76g/L (calculated by calcium chloride) are obtained through clarification, filtration and washing, 119.31g of calcium chloride dihydrate product is obtained after the filtrate is concentrated and spray-dehydrated at 120 ℃, the calcium chloride content (mass fraction) is 77.9%, the total magnesium content (mass fraction calculated by magnesium chloride) is 0.0052%, the iron content is 0.00008%, the heavy metal (Mg/kg calculated by Pb) is 15, the calcium content and the impurity content meet the requirements of national GBT 26520 one-grade industrial anhydrous calcium chloride, and the calcium content and the heavy metal content 2011 meet the requirements of GB1886.45-2016 food-grade calcium chloride.

Examples 4-6 preparation of high purity anhydrous calcium chloride

The method for preparing high-purity anhydrous calcium chloride in examples 4 to 6 includes the following steps:

(1) adding calcium hydroxide-containing slurry into magnesium chloride-containing wastewater generated by extraction treatment in the metal smelting separation process, uniformly mixing, carrying out alkali conversion reaction, and filtering to obtain a high-purity calcium chloride solution with extremely low content of non-calcium impurity elements and a magnesium hydroxide filter cake;

(2) and concentrating the prepared high-purity calcium chloride solution, and performing spray dehydration to obtain a high-purity anhydrous calcium chloride product.

The parameters and raw materials for preparing anhydrous calcium chloride in each example are shown in Table 3 below, and the product indexes of the prepared anhydrous calcium chloride product are shown in Table 4 below.

TABLE 3 parameters and raw materials for the preparation of anhydrous calcium chloride

TABLE 4 product index of the anhydrous calcium chloride product

Taking the parameters in the above example 6 as examples, the method for preparing high-purity anhydrous calcium chloride comprises the following steps: 500g of limestone is roasted at 930 ℃ for 3h to obtain calcium oxide-containing powder, 110g of the calcium oxide-containing powder is taken to be digested and reacted with 1L of pure water for 1h to obtain calcium hydroxide slurry with the calcium content (calculated by calcium oxide) of about 100 g/L. 500mL of prepared calcium hydroxide slurry is mixed and reacted with 350mL of rare earth smelting magnesium chloride solution with the concentration of 2.5mol/L, in the reaction process, the molar ratio of the added magnesium chloride to the added calcium oxide is Mg/Ca of 0.98, the reaction time is 1h, the reaction temperature is 50 ℃, the filtrate is clarified, filtered and washed to obtain 131g of magnesium hydroxide filter cake and 955mL of calcium chloride filtrate with the concentration of 94.76g/L (calculated by calcium chloride), the filtrate is concentrated and subjected to spray dehydration at 300 ℃ to obtain 87.33g of calcium chloride dihydrate product, the calcium chloride content (mass fraction) is 97.9%, the total magnesium content (calculated by magnesium chloride, mass fraction) is 0.0057%, the iron content (mass fraction) is 0.00009%, the heavy metal (calculated by Pb, Mg/kg) is 17, the calcium content and the impurity content meet the requirements of national GBT 26520-rich industrial anhydrous calcium chloride, and the calcium content and the heavy metal content 2011 meet the requirements of GB1886.45-2016 food-grade calcium chloride.

EXAMPLE 7 preparation of high purity calcium carbonate

The method for preparing high purity calcium carbonate of example 7 comprises the following steps:

grinding the anhydrous calcium chloride obtained in the example 6 to 200 meshes, taking 80g of the anhydrous calcium chloride to carry out pyrolysis reaction in a pyrolysis furnace, wherein the reaction temperature is 930 ℃, the reaction pressure is 0.2MPa, and the volume fraction ratio (X) of hydrogen chloride to steam in the reaction process_{Hydrogen chloride})²/X_{Steam of water}＝15.3×10^-5And the reaction time is 1.5h, 73.5g of calcium oxide powder is prepared, and the tail gas is recovered to prepare 298mL of 15.5 percent hydrochloric acid. 50g of the obtained calcium oxide powder is taken, is mixed with pure water to prepare 120.3g of calcium carbonate powder by a carbonization method, wherein the content of calcium carbonate is 98.32 percent, the total magnesium content (calculated by magnesium oxide, mass fraction) is 0.0027 percent, and the characterization parameters of the particle size, the specific surface area and the like of a scanning electron microscope meet the requirements of GBT 19590-;

washing the magnesium hydroxide filter cake obtained in the alkali conversion process of the embodiment 6 with water for multiple times, then using water to prepare slurry to 7.5g/L (calculated by MgO), introducing 85% (volume fraction) carbon dioxide gas (a certain amount of industrial liquid carbon dioxide is supplemented by mixed carbon dioxide generated in the roasting process) into the magnesium hydroxide slurry under normal pressure, controlling the pH of the carbonization reaction end point to be 7.1, controlling the reaction temperature to be 40 ℃, controlling the reaction time to be 35min, and obtaining 7.0g/L (calculated by MgO) of magnesium bicarbonate solution and a small amount of carbonized slag through filtering;

pretreating the obtained magnesium bicarbonate solution with an organic phase of 1.5mol/L P507 by comparing O/A (3/4) with that of an organic phase to obtain a magnesium-containing loaded organic, extracting the magnesium-containing loaded organic with a lanthanum chloride solution of 1mol/L by using O/A (3/4) to obtain a lanthanum-containing loaded organic containing 0.17mol/L lanthanum, and back-extracting the lanthanum-containing loaded organic with 15.5% hydrochloric acid (a by-product obtained in the embodiment) by using O/A (1/1) to obtain a lanthanum chloride back-extraction solution;

mixing the obtained lanthanum chloride aqueous solution with the obtained magnesium bicarbonate solution to precipitate rare earth, filtering and drying to obtain lanthanum carbonate powder, and roasting at high temperature to obtain a lanthanum oxide product with the purity of 99.99 percent.

Examples 8 to 10

The process for preparing high purity calcium carbonate of examples 8-10, like example 7, includes the following steps:

(1) adding calcium hydroxide-containing slurry into magnesium chloride-containing wastewater generated by extraction treatment in the metal smelting separation process, uniformly mixing, carrying out alkali conversion reaction, and filtering to obtain a high-purity calcium chloride solution with extremely low content of non-calcium impurity elements and a magnesium hydroxide filter cake;

(2) concentrating the prepared high-purity calcium chloride solution, and performing spray dehydration to obtain a high-purity calcium chloride product; the obtained magnesium hydroxide filter cake is carbonized to prepare a magnesium bicarbonate solution; and collecting the water vapor produced in the spray dehydration step;

(3, selecting the high-purity calcium chloride product prepared in the embodiment 1-6 to carry out pyrolysis reaction to obtain high-purity calcium oxide powder and hydrogen chloride gas, carrying out pyrolysis reaction on the water vapor collected in the step (2), and collecting the water vapor in the pyrolysis reaction;

(4) condensing the water vapor collected in the step (3) to obtain water, adding the prepared high-purity calcium oxide powder for size mixing, and carrying out carbonization reaction to obtain high-purity calcium carbonate; the obtained hydrogen chloride gas is prepared into hydrochloric acid;

(5) recycling the magnesium bicarbonate solution prepared in the step (2) and the hydrochloric acid prepared in the step (4) to the metal smelting separation process in the step (1) for extraction and separation to obtain the magnesium chloride-containing wastewater and carbon dioxide; and the obtained carbon dioxide is used for the carbonization reaction involved in the whole reaction to realize the circulation of the whole process.

The parameters and raw materials for preparing high purity calcium carbonate in each of examples 8-10 are shown in Table 5 below, and the product specifications for the calcium carbonate products are shown in Table 6 below.

TABLE 5 parameters and raw materials for the preparation of calcium carbonate

TABLE 6 parameters and raw materials for the preparation of calcium carbonate

From the data of the above examples, it can be seen that compared with comparative products at various stages, the method for preparing high-purity calcium product according to the method effectively solves the problem of the influence of impurities on the product quality in the preparation of calcium chloride dihydrate, anhydrous calcium chloride and high-purity calcium carbonate, and improves the stability of the calcium chloride dihydrate, anhydrous calcium chloride and calcium carbonate products; meanwhile, the resource recycling is realized, and no wastewater or waste gas is discharged in the whole process.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.